Development of polyelectrolyte multilayer thin film composite membrane for water desalination application

• The use of spin assisted layer by layer assembly (SA-LbL) for membrane preparation
• Development of the SA-LbL protocol to fabricate thin film on polymeric substrate
• PAH/PAA membrane fabricated using SA-LbL shows stability for long term use.
• PAH/PAA membrane transport mechanism follows solution diffusion model.

Thin film composite membranes were fabricated via spin assisted layer by layer (SA-LbL) assembly by depositing alternate layers of poly(allyl amine hydrochloride) (PAH) and poly(acrylic acid) (PAA) on a polysulfone (PSF) ultrafiltration membrane as support. The suitability of these membranes for potential water purification applications was explored by testing the stability of the deposited thin films and their permeation characteristic using cross-flow permeation cell. Permeation test conducted at a pressure of 40 bar, temperature of 25 °C, pH of 6 and feed water concentration of 2000 ppm NaCl demonstrated that the PAH/PAA multilayer film deposited on polysulfone support remained stable and intact under long-term test conditions. The 120 bilayers of PAH/PAA membrane tested at the above condition showed flux of 15 L/m2.h and salt rejection of 65%. The membrane performance evaluation also revealed that SA-LbL PAH/PAA membrane follows the characteristics of the solution diffusion membrane.